Tensioning device for drive chains



Feb. 12, 1929.

F. L. MORSE TENSIONING DEVICE FOR DRIVE CHAINS Filed Dec. 8, 1925 2 Sheets-Sheet 1 IN VENTOR W1C m F. L. MORSE TENSIONING DEVICE FOR DRIVE CHAINS Filed Dec. 8, 1925 2 Sheets-Sheet 2 lIII/IIII/I/l) IN VEN TOR Patented Feb. 12, .1929.

, UNITED STATES 1,701,820 PATENT OFFICE.

FRANK L. MORSE, OF ITHACA, NEW YORK, ASSIGNOR '10 MORSE CHAIN COMPANY, 01'

' ITEAGA, NEW YORK, A CORPORATION OF NEW YORK.

TENSIONING DEVICE FOR DRIVE CHAINS.

Application filed December which is simple in construction, automatic in action, and approximately uniformly effective for all adjustments, and one which may be readily applied as a unit either to new or existing apparatus.

The nature and objects of my invention will be more readily understood when it is considered that in devices for taking up slack" in drive chains, it is customary to mount the sprocket taking up the slack on an eccentric, which eccentric is adjusted by a tensioning means in association therewith which automatically operates to take up slack as" it occurs. It is obvious that the leverage of the eccentric varies as the eccentric is shifted, consequently resulting in a change in, the forces. In this connection, it is also pointed out that the tensioning value of the springs ordinarily employed as the tensioning means changes for difierent positions of adjustment of the device with the objectionable results here following.

Due to this change in tension of the spring, it will be seen that in order to'exert sufficient tension on the chain at its maximum adjustment, the tension when initially installing the device, that is, when the run of chain operated on to take up slack is more nearly straight, mustnece ssarily be greater than actually needed at this point. The change in leverage of the eccentric also makes it necessary to increase the tension over that needed to have effective tension at installation. The result is that drives employing such tensioning devices are often n'olsy, a peculiar ob ectionable whirring sound existingat the point where the chain leaves the s, 1925. Serial No. 74,088.

in tension of the tensioning means, which, in the Preferred form of my invention, I have shown as a compensating eccentric associated with the sprocket eccentric, through the medium of which compensating eccentric the tensioning means operates approximately uniformly, as will appear in the description of my invention.

How the foregoing, together with such other objects as may hereinafter appear, or are incident to my invention, are realized, is illustrated in preferred form in the accompanying drawings, wherein- Fig. 1 is' a diagrammatic elevation of a typical fronteend layout for automobiles with my invention applied thereto;

Fig. 2 is an elevation view of my tensioning device with some of the parts in section, and with the sprocket wheel removed;

Fig. 3 is a plan view of my device with a portion of the gear housing and the sprocket wheelshown in section;

Fig. 4 is a section taken on the line H of Fig. 2; and

Figs. 5 and 6 are diagrammatic views of two positions of the device.

Referring to the drawings, it will be seen that in Fig. 1 a front end drive of the usual triangular arrangement is diagrammatically shown, which drive consists of the crank shaft sprocket 5, the accessory shaft sprocket 6, and the 'cam shaft sprocket 7 connected together and driven in a clockwise direction by the chain 8. T have'shown a tensioning device A preferably located between the sprockets 5 and 6 which acts on the run of chain therebetween to take up slack as it occurs.

This tensioning device comprises a movable eccentric 9 mounted on the stub shaft 10, which shaft is secured to the gear housing 11. The eccentric 9 has rotatably mounted there- 'on the sprocket wheel 12 adapted to engage the chain 8, from which it will be seen that as the eccentric is moved from its initial position indicated in Figs. 1, 2 and 5, the sprocket wheel 12 is moved therewith to take up the slack in the chain. Movement of the eccentrio is accomplished by means of a tensioning stub shaft 10, which eccentric is angularly disposed to the eccentric 9, and secured to move therewith, and it is through the medium of this eccentric 14 that connection bet-ween the spring 13 and the eccentric 9 is made as will now appear.

The spring 13 has its inner end 15 secured to the stud 16 of the arm or bracket 17, which bracket is adjustably secured between the shoulder 18 on the shaft 10 and the gear housing 11 by means of the nut 19. The other or outer end 20 of the spring is secured to the drum 21. The drum 21 is provided with spaced slots 22 into one of which the hooked end 23 of the band or strap 24 is inserted, the other end of said strap being secured to the second eccentric 14 at a pointremote of the point of contact between the eccentric and strap; in other words, the strap is wrapped partly around the eccentric and then secured thereto. From inspection of Fig. 3, it will be seen that the eccentric 14 and the drum 21 lie in substantially the same plane.

In this connection it is pointed out that the second eccentric 14 is so disposed with relation to the eccentric 9 that the band 24 contacts with said eccentric 14 at a point intermediate its hi h and low points when the eccentric 9 is at its low point, or initial position i as shown in Figs. 1, 2 and 5. By virtue of this angular disposition of one eccentric to the other, it will be seen that the leverages of both eccentrics increase for the first 90 degrees of travel and decrease for the next 90 degrees of travel whereby to obtain the above noted resu ts.

. From the foregoing, it will be apparent that the spring 13 tends to rotate the drum 21 in the direction of the arrow (see Fig. 2), which, in turn, tends to rotate the eccentric 9 through the medium of the strap 24 and the eccentric 14, thus causing the sprocket wheel 12 to be held against the chain under the tension of the spring. The tension of the spring may be adjusted by rotating the drum until the springis wound up to the value desired, the hook 23 being then inserted in the nearest notch 22 It is pointed out that as the eccentric 9 is moved to take up ark in the chain, the leverage thereof increases. which. unless otherwise compensated for, would reduce the value of the force exerted by the spring as adjustments take place. Byattachingthe spring to the eccentric 14. as hereinbefore described, I maintain a substantially constant tension on the chain, because as the leverage of the eccentric increases so does the leverage of the eccentric 14. The eccentric 14, in addition to compensating for the change in leverage of the eccentric 9, also serves to compensate for the decreasing tension of the.

\ tricity greater than that of the eccentric 9,

or by making the eccentric surface thereof in the form of a cam.

In order to prevent the eccentric 9 returning to positions of looser adjustment, I have provided the ratchet wheel which, in this instance, is formed as part of said eccentric and eccentric with the shaft or stud 10. A spring latch 26 is mounted on the arm 17 for engaging the ratchet wheel. It is here mentioned that other forms of springs may be used to, obtain the desired results.

lVhile I have described the second eccentric 14 as preferably secured to the eccentric 9, it is pointed out that the drum 21 may be made in the form of an eccentric to obtain the results hereinbefore described.

It is also pointed out that my invention may be applied directly to one of the shafts of the drive, as, for instance, to the accessory shaft, in which case a coupling device would be introduced between the sprocket and the shaft.

By mounting the spring 13 with its drum 21 on the arm 17, I am enabled to convenient- 1y adjust the tension of the spring and to readily make a replacement in case of a spring failure. The adjustability of the arm enables me to adjust it to any convenient position.

What I claim and desire to secure by Letters Patent is 1. In a tensioning device for drive chains, a wheel, an eccentric on which said wheel is mounted, spring means for rotating said eccentric to shift the sprocket wheel to take up slack in the chain, and means compensating for both the change in leverage in the eccentric and change in tension of the spring means to maintain approximately constant tension. 2. A tensioning device for drive chains including a sprocket wheel, a movable eccentric on which said wheel is rotatably mounted, an eccentric-like member an 'ularly disposed to said movable eccentric an movable therewith, resilient means, and a hand between said resilient means and the eccentric-like member wrapped partly therearound and attached thereto.

3. A tensioning device including movable means adapted to engage an element to-which tension is to be applied, and means for moving said movable means including cam means operating to maintain-the value of the tension approximately constant for all adjustments and serving as a connection between the movable and the moving means.

4. A self contained tensioning device for drive chains including a shaft, an eccentric mounted thereon, a wheel mounted on said eccentric, and resilient means for rotating said eccentric to shift the wheel to take up slack in the chain including cam means operating to maintain the value of the tension approximately constant for all adjustments.

5. In combination, a drive chain, a-sprocket wheel engaging said chain, a movable eccentric mounting for said wheel, a second eccentric associated with the eccentric mounting, and means for moving the eccentric mounting, through the medium of said second eccentric.

6. In a tensioning device for drive chains, a wheel, an eccentric on which said wheel is mounted, means for rotating said eccentric to shift the wheel to take Up slack in the chain, and a mechanical advantage connection between said means and the eccentric, including a cam associated with said eccentrio, and a member connecting the eccentric rotating means with said cam at the cam surface thereof.

7. In a tensioning device for drive chains, a wheel. an eccentric on which said wheel is mounted, means for rotating said eccentric to shift the wheel to take up slack in the chain, and amechanical advantage connection between said means and the eccentric, including a cam associated with said eccentric, and a member connecting the eccentric rotating means with said cam at the cam surface thereof, together with means for holding the eccentric in positions of adjustment.

8. In a tensioning device for drive chains, a sprocket wheel, a movable eccentric on which said wheel is mounted, cam means movable with said eccentric, and spring means associated with said cam means for moving the cam means and the eccentric to take up slack in the chain, said cam means'operating to maintain the value of the tension approximately constant for all adjustments.

9. In a tensioning device for drive chains, a sprocket wheel, a movable eccentric on which said wheel is mounted, cam means movable with said eccentric, and spring means associated with said cam means for moving the cam means and the eccentric to take up slack in the chain. the leverage of the cam means automatically altering as the leverage of the eccentric varies to produce substantially constant tension for all positions of adjustment.

In testimony whereof I have hereunto signed my name.

FRANK L. MORSE.

CERTIFICATE @h CQRREGIMN.

Patent No. 11, 7M, 8261?.

Granted hehraary i2, 392%, to

FRANK 1L. lhlth lit is hereby certified that error appears in the ahove nurnherecl patent word "eccentric" read "concentric";

"wheel" first occurrence insert the word Signed and sealed this Nth (Seal) printed specification ot the requiring? correction as tollowe: Page 2., line 72, for the sarnc'nage, line 98, claim it, hctore the were! "sprocket"; and that the said Letters Patent should he read with these corrections therein that the some to the record or the case in the Patent @ttice.

day of March, A. D. 11929.

may conform hi. 3. Moore, Acting Corissioncr of Patents.

CERTIFICATE 0i? GQRREGTION.

l a -tent No. 1,701,820. Granted February 12, 1929, to

FRANK L. MORSE.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 2, line 72, for the word "eccentric" read "concentric"; same page, line 98, claim 1, before the word "wheel" first occurrence insert the Word "sprocket"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of March, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents. 

